1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device, and more particularly to an LCD device with improved high transmittance and high contrast.
2. Description of Related Arts
An LCD device controls the light transmittance by using the characteristic that liquid crystal (LC) molecules present different light polarization or refraction effects under different alignments so as to produce images. A twisted nematic (TN) LCD device has good light transmittance but an extremely narrow viewing angle as influenced by the structure and optical characteristic of the LC molecules.
To solve the transmittance and viewing angle problems, a twisted vertical alignment model has been proposed so as to provide the high transmittance and the wide viewing angle. However, because the LC molecules are aligned in a vertical alignment manner, when the LC molecules are applied with a low voltage and the LCD device is watched at an inclined viewing angle, a gray-level inversion problem occurs, which causes the problem of color shift at an inclined viewing angle and influences a normal presentation of images of the LCD device.
To resolve this issue, two or more alignment domains are formed in the same pixel to form multi-domain vertical alignment (MVA) LCD device so as to eliminate the gray-level inversion problem and increase the viewing angles. In practice, three specific methods are provided. In the first method, one pixel is divided into multiple display areas, and every display area forms a different voltage by means of capacitive coupling, thereby producing the alignment effect of multiple display areas. In the second method, one pixel is divided into multiple display areas and two thin film transistors are used to make each display area form a different voltage, thereby solving the gray-level inversion problem. In the third method, the pixel is divided into two or more display areas and an electronic barrier material is covered above a part of the electrode of the display area, thereby producing the alignment effect of multiple display areas.
However, the methods for solving the gray-level inversion problem in the prior arts have complicated LCD device processes. In view of the above, it is the subject of the present invention to provide a simple method with improved high transmittance and high contrast ratio so that the LCD device can present optimal images.